The present invention relates to a seat belt apparatus for a vehicle.
A seat belt apparatus for restraining an occupant seated in a vehicle seat with a webbing belt may have a long band shape including a retractor (e.g., a winding device) disposed on the vehicle seat or a vehicle body. The retractor includes a spool (e.g., a winding shaft) onto which the webbing belt is wound up and a spring for biasing the spool in a winding direction of the webbing belt.
A retractor may have a motor for restraining an occupant's body during sudden turning or sudden braking and for removing slack of the webbing belt relative to the position of the occupant. The driving force of the motor is transmitted to a spool to rotate the spool by a predetermined amount in the winding direction of the webbing belt to temporarily increase the tension on the webbing belt. If the spool and the driving shaft of the motor are always mechanically connected to each other, the normal winding and unwinding actions of the webbing belt may be affected causing unnecessary load on the motor. To avoid an unnecessary load, a clutch mechanism is usually arranged between the driving shaft of the motor and the spool.